If you are creating a form for your application you might need some validation on components before submitting. Wicket has some methods (e.g setRequired(true)) which can help you with that. In this article I will show you the setType method. This method will prevent you to submit the form when e.g. the input field is not filled in correctly. An example could be when your users have to fill in a double as number. If the user fills in something else it will show a warning in the feedbackpanel. See java example below how to deal with this.